1. Field of the Invention
The field relates to a recordable optical information recording medium, such as a DVD-R, DVD+R, Blu-ray Disc or HD-DVD, capable of recording and reproducing information by a laser with respect to a dye and a rewritable optical information recording medium such as a DVD-RAM or DVD-RW, and particularly to a new medium structure to record information for copyright protection or the like.
2. Description of the Related Technology
A DVD includes a main information recording area in which a moving picture and the like are recorded, and a sub-information recording area or a control information recording area in which sub-information and the like are recorded for the purpose of copyright protection or the like. In CPRM (Content Protection for Recordable Media) as copyright protection technology adopted in DVD standards, a specific bar code is formed in the NBCA (Narrow Burst Cutting Area) of a disc on which main information is recorded. Although copyright protection management by the CPRM as stated above has not been performed in a recordable disc such as a DVD-R or a rewritable optical disc, such management has been requested from the viewpoint of copyright protection and countermeasures against copyright infringement. However, when the technology of the DVD is attempted to be directly applied to the optical disc, although the length of the bar code and the recording part on the disc have already been determined by the standard, its physical shape (or structure) is not definite, and accordingly, there is no suitable method under the present circumstances. However, it is important to perform copy control effectively and with high accuracy from the viewpoint of copyright protection, and an effective physical shape of the bar code relating to the CPRM in the optical disc is needed.
As the related art concerning such bar code shape, there is an optical disc and an optical disk reproduction apparatus disclosed in patent JP-A-2001-110062. This has an object to facilitate the formation and reproduction of a bar code, and is characterized in that a stripe-shaped mark long in the radial direction is formed in a specific annular area not used for the recording of main information, and the width of the mark is made a half or less of a mark period.
However, the related art disclosed in JP-A-2001-110062 substantially relates to a ROM optical disc, where a reflection film formed on a substrate is fused, and since a difference in thermal expansion coefficient between the substrate and the reflection film is excessively large, when the reflection film is deformed, it is peeled off and a gap is produced. This has an influence on jitter (fluctuations) at the time of data readout, and there is error because the jitters can not be sufficiently suppressed.
In addition, recently, the speed of recording and reproduction of data to and from the optical disc has been increased, and a bar code formation method is needed which can sufficiently deal with the increased speed so that defective readout or the like does not occur even at the time of high speed.